To meet the demand for wireless data traffic having increased since deployment of 4G (4th-Generation) communication systems, efforts have been made to develop an improved 5G (5th-Generation) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’. The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation, and the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications.
In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, Machine Type Communication (MTC), and Machine-to-Machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud Radio Access Network (RAN) as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology.
Recently, a multiple input multiple output (MIMO) system that utilizes resources of a space area in order to transmit high quality data at a high speed in a wireless communication environment has been widely researched. More particularly, the technology of massive MIMO that adopts dozens to hundreds of antennas in a base station draws attention. The massive MIMO system adopts signal transmission devices, for example, a multitude of antennas installed in a base station (BS), and easily copes with various issues, such as fast fading, and inter-user interferences using only a simple linear pre-coder, in order to thereby obtain a high data rate. The massive MIMO system is not limited to the number of antennas supported by the base station, and it is based on that the base station thereof knows the channel information of every antenna supported by the base station. The MIMO system may be divided into a single-user (SU) MIMO type in which a single user uses all of the same time and frequency resource, and a multi-user (MU) MIMO type in which a plurality of users shares the same time and frequency resource through space multiplexing.
With regard to the SU-MIMO type, a method by which the principal singular vector of a channel is quantized to be transmitted for channel feedback, like the Grassmanian code book, has been developed and discussed in various organizations for standardization, such as Institute of Electrical and Electronics Engineers (IEEE) 802.16.
Since cooperation between users cannot be made in the MU-MIMO type, interferences between receivers (users) should be removed or attenuated only by a pre-coder that is used in the base station. In addition, each receiver should feed channel information back to the base station so that the base station creates the pre-coder for multiple users. The MU-MIMO type adopts an explicit feedback method in which the channel information is directly transmitted, and an implicit feedback method by which the receiver selects a pre-coding matrix indicator (PMI) to be transmitted to the base station.
Typical technologies of channel feedback are limited to the number of antennas and designed for a system that has a relatively low channel space correlation. However, in the case of the massive MIMO system, dozens to hundreds of antennas should be installed in the limited space, so the space correlation thereof may be higher than that of a typical system. In addition, the feedback method of transmitting the PMI from the receiver to the base station is not suitable for the massive MIMO environment that has a high space correlation.
Therefore, a need exists for an apparatus and a method of channel feedback, which reduces overhead of channel feedback and lowers complexity in a multi-antenna system that has a relatively high space correlation.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.